Historically, in flexographic printing, flat, flexible printing plates, fabricated from photopolymers, were hand mounted onto print cylinders by wrapping the printing plate around the cylinder and adhering it there with using various methods such as clamps, tape, magnets or other similar devices. This process works well, but is labor intensive and great care must be taken to ensure that the registration of the plate on the cylinder is accurate. Typically, a compressible material is inserted between the print cylinder and the printing plate to allow for additional compression during the print process.
In the context of the foregoing printing process, cylindrical printing sleeves could be used to increase the diameter of standard print cylinders to fit various printing jobs. In this case the printing sleeve is fitted over the print cylinder and then the printing plate, and the compressible material if used, is mounted on the printing sleeve. The use of printing sleeves in this manner allows the use of one standard printing cylinder (which are fabricated from high strength metals and are expensive) to be used on a wide variety of print jobs. In this regard, please refer to U.S. Pat. No. 4,903,597, the teachings of which are incorporated herein by reference in their entirety.
Hollow cylindrical sleeves of various configurations are known from U.S. Pat. Nos. 4,391,898; 4,503,769; 4,554,040; 4,601,928; 4,656,942; 4,812,219; 4,949,445; 4,963,404; 5,468,568; 5,819,657; 5,840,386; 6,038,971; and 6,038,975, the teachings each of which are incorporated herein in their entirety. Generally, these sleeves are comprised of a variety of layers of materials optimized for specific effects.
Efforts have been made to combine the printing plate with the printing sleeve. For instance, a product is offered by OEC Graphics, Inc. under the trademark, SEAMEX™, wherein a flat photopolymer printing plate is bonded using heat to a printing sleeve. Problems arise with this process, however, in trying to eliminate the seam caused by the joining of the ends of the flat printing plate. Additionally, the SEAMEX™ process is long and labor intensive. Degradation of image fidelity may also result due to heat history the photopolymer is subjected to.
Published U.S. Patent Application 2003/0157285 to Busshoff discusses a printing sleeve that has a photoimageable material disposed on the surface of the sleeve. It is believed, however, that the printing quality of the sleeves made in accordance with Busshoff suffers, because of poor adhesion of the photoimageable material to the printing sleeve surface. Adhesion issues are particularly troublesome when the photoimageable material is imaged to create fine detail features which are separated from other portions of photoimageable material when developed. In this case, poor adhesion of these fine, stand alone features, will cause a loss of fidelity in printing.